Spread of the Pacific Oyster Crassostrea gigas in the Wadden Sea

Causes and consequences of a successful invasion

The Pacific Oyster has spread over the entire Wadden Sea. Results from ongoing research projects have indicated that spreading of the Pacific oyster has increased considerably during the last 5 years. In order to obtain an up-date of the status of the Pacific oyster invasion and to assess the possible consequences for the ecosystem, as well as for monitoring and management, also with regard to the EC Habitats and Water Framework Directive, a trilateral report with a comprehensive data analysis was compiled by Georg Nehls and Heike Büttger (BioConsult SH) on behalf of the Common Wadden Sea Secretariat.

The work was co-funded by the Interreg IIIB project HARBASINS and supported by the Research Institute Senckenberg (Wilhelmshaven), the Schleswig-Holstein National Park Agency (Tönning) and the Lower Saxon National Park Administration (Wilhelmshaven). Additionally, the Institute for Marine Resources & Ecosystem Studies (IMARES, Texel), the Danish Fisheries Research Institute and the Alfred-Wegener-Institute (AWI, List/Sylt) provided recent data on oyster distribution.

The report was the starting point for a discussion at a trilateral workshop on 22 March 2007 in Wilhelmshaven with scientists and managers from the Wadden Sea and England to discuss the recent status and possible consequences of the Pacific oyster spreading in the Wadden Sea and to prepare recommendations regarding follow up-activities in the fields of research, monitoring and management. The workshop program is in Annex 1 and the list of participants is in Annex 2.